Array.prototype.duplicateRemoval = function() {
	let newArr = [];
	let o = {};

	for(item of this){
		if(!o[item]){
			o[item] = true;
			newArr.push(item);
		}
	}
	return newArr;
};

console.log([1,2,3,1,2,3,4,1,2,5,7].duplicateRemoval())